The present invention relates to a device for metered delivery of a liquid or viscous substance to a consumption point and, in particular, to a device for metered delivery of a liquid or viscous lubricant to a lubrication point.
A regular delivery of a lubricant to lubrication points of machines and apparatuses is an important factor in reliable operation of the machine or the apparatus and in preventing wear of machine or apparatus parts. An interruption in the lubricant delivery can result in a damage of the machine or the apparatus and in increased losses.
Large machines and apparatuses often have many lubrication points which should be lubricated with grease or lubricating oil in accordance with a predetermined lubrication plan. In many machines and apparatuses, even nowadays, the lubrication is effected manually which, on one hand, increases the production costs and, on the other hand, is not very reliable. Therefore, there exists a need for automatization of the lubrication process.
One possible way of solving the problem of automatic lubrication is the use of a central lubrication system which insures delivery of a lubricant to all lubrication points of a machine or an apparatus. However, the use of a central lubrication system means imposing additional limitations on the machine or apparatus design because, with the use of a central lubrication system, as a rule only one lubricant substance is available. Therefore, separate lubrication points cannot be designed in an optimal manner. Further, the use of a central lubrication system increases the investment costs and, because of a rather complicated structure of the central lubrication system, it is not always reliable.
Therefore, numerous devices have been developed for automatic lubrication of each separate lubrication point of a machine or an apparatus. These devices insure delivery of different lubricants to different lubrication points of the same machine or apparatus.
The devices for lubricating separate lubrication points generally includes a cylinder, in which a lubricant is stored and from which the lubricant is delivered slowly by a spring-biased piston, displaceable in the cylinder, through an appropriate orifice. However, the known devices have many drawbacks.
Specifically, when lubricants having a mineral base are used, e.g., such as grease, their viscosity changes with a change in temperature and, to a lesser degree, with a change in pressure. At high temperatures, the viscosity and thereby the flow resistance is reduced so that in the same time period, more lubricant will be delivered to a lubrication point than that at low temperatures. This temperature-dependence can result, at high temperatures, in an early emptying of the device. At low temperatures and, thus, at high viscosity, the delivery of a lubricant can be interrupted.
Another drawback of known devices consists in that the lubricant, during the entire period of the use of the device, which can last several months, is subjected to a spring-biasing force. For many lubricants, such a lasting loading leads to separation of the lubricant components and, in particular, to the separation of an oil containing in grease. This can adversely affect the lubrication characteristics of a lubricant.
A further drawback consists in the dependence of the lubricant delivery on the characteristics of a spring acting on the piston. Because conventionally used springs have an approximate linear characteristic, the spring force with spring expansion is reduced, so that the pressure applied to the lubricant is also reduced. This results in a reduction of the amount of lubricant delivered in a unit of time.
A still further drawback of the known devices consists in that the delivered amount of the lubricant does not depend on mutual interaction between the spring force, viscosity and orifice effective resistance, but depends rather on the flow resistance of the lubricant inside a machine or an apparatus, the flow resistance in the path leading to the lubrication point. This substantially complicates the selection of a correct spring stiffness.
Some of the drawbacks of the conventional lubricating devices are eliminated in a device disclosed in International Publications WO 88/09899 and WO/09900. The device disclosed in these publications includes a chamber for receiving a lubricant and separated by a displaceable insert from another chamber which contains a gas-charging element, for example, a cell consisting of an anode, a cathode and an electrolyte. The gas pressure forces the lubricant through an orifice and provides for flow of the lubricant to the lubrication point.
In the device disclosed in the International publications WP88/09899 and WO88/09900, the negative influence of the spring characteristic of the loading spring on the amount of the delivered lubricant is eliminated. However, in the disclosed device, the amount of the delivered lubricant still depends on the temperature. Further, a danger of the separation of the lubricant components under a constant spring loading still exists.
Another important drawback of the known lubricating device consists in that it is difficult to adapt the lubricant delivery to each lubrication point because separate lubrication points have different requirements for the amount of a lubricant. Therefore, it is necessary to provide a plurality of lubricating devices for accommodating different lubricating requirements. This not only complicates the storage of the devices but presents a danger of mixing the devices, which may result in over- or, which is worse, under-supply of a lubricant to a particular lubrication point.
U.S. Pat. No. 2,856,024 discloses a device for metered delivery of one of a liquid substance and a viscous substance to a consumption point, including a container for receiving an amount of the one of a liquid substance and a viscous substance, delivery means comprising a chamber for receiving the container, a displacement element displaceable between first and second positions for enabling flow of the one substance from the container to the consumption point, and drive means for displacing the displaceable element between the first and second positions.
The device disclosed in U.S. Pat. No. 2,856,024 can be used for a centralized delivery or separate point delivery, and it includes a spring-driven piston, which functions as a displacement element and provides for flow of the lubricant from the container into a lubricant conduit or to the lubrication point. The disclosed device further comprises means for displacing the piston against the spring-biasing force. The displacing means include a shaft driven by a machine drive of a lubricated machine.
An object of the invention is a device for metered delivery of a liquid or viscous substance and which insures a precise metering of a predetermined amount of a lubricant, which corresponds to the requirement of the lubrication point and further insures that a selected amount of the lubricant to be delivered to the lubrication point is maintained substantially constant.
This and other objects of the invention, which will become apparent hereinafter, are achieved by providing a lubricating device, including connection means, which are separate from the delivery means and are securable to the consumption point for communicating the delivery means with the consumption point. The connection means includes an indicator indicating a predetermined amount of the one substance to be delivered to the consumption point in a unit of time. There is further provided control means for controlling operation of the drive means, in accordance with information provided by the indicator, so that the predetermined amount of the one substance is delivered to the consumption point in the unit of time.
The delivery device comprises an energy accumulator which is driven by the drive means against an elastic restoring force from a first position, in which the restoring force is small, to a second position with a high restoring force. The restoring force in the second position of the energy accumulator is so high that it insures flow of the lubricant through the delivery device.
As the energy accumulator, a spring is used. The spring acts on a piston which functions as the displacement member. The piston insures delivery of a precise volume to the lubrication point and, thus, precise metering. The piston advantageously cooperates with a stop which limits the delivery volume. The stop is advantageously adjustable so that the delivery volume can be adapted to particular requirements of the lubrication point.
A further advantage of the inventive device consists in that the delivery volume does not depend on the properties of the deliverable substance and on the environmental conditions of the lubrication point. This enables delivery of the desired amount of the substance in a unit of time.
The important advantage of providing a stop consists in that the stop can be provided in an element separate from the delivery means. In a preferred embodiment of the invention, this separate element is directly connected with the lubrication point, e.g., it can be screwed into the nipple of the lubrication point. When the lubricant container is replaced, this element remains in the machine so that the replacement does not influence the delivery volume.
Using a stop enables to insure, with the use of an appropriate container, a delivery duration, for example, of 100, 200, 300 and 400 days. The stop is adjusted for a desired volume, and the element is screwed into a lubricant inlet of the lubrication point. Thus, it is insured that at each replacement or filling of the container, the same amount of lubricant is delivered to the lubrication point.
The control of the delivery volume per unit of time can be effected by changing the time interval between two successive delivery strokes. In this case, the separate element is provided with an indicator indicating the time interval between two successive delivery strokes. The separate element can also be provided with two indicators, one of which defines the length of the piston stroke and, thus, the delivery volume per stroke, and the other of which indicates the time interval between two successive delivery strokes.
The delivery means and the drive means are so designed that the piston automatically returns from the second position to the first position. This is insured, as it has already been discussed, by providing an energy accumulator in the form of a return spring acting on the piston.
The advantage of using an energy accumulator consists also in that only a short-duration pressure is necessary for delivering the substance from the container. For example, when the time interval between two substance delivery stroke is twelve hours, the substance is subjected to the pressure only for several seconds or minutes daily. This reliably prevents separation of the substance components. In addition, the reliability of the lubrication is increased, and it is possible to admix into the substance component separation-preventing substances.
Further, the return force of the energy accumulator or the spring is always greater than that required for insuring delivery. This insures a rapid delivery of the substance from the container to the lubrication point and eliminates dependence of the delivery on the environmental conditions. If the low temperature prevails and, therefore, the viscosity of the substance is increased, the return force, being high, substantially reduces the substance shear rate. It only means that at low temperatures, for the delivery of a predetermined volume, the delivery time is somewhat increased in comparison with a delivery time at higher temperatures, e.g., from two minutes at a high temperature, to three minutes at a low temperature. However, the volume delivered in a unit of time, in a predetermined time interval, does not increase. The reverse holds true for the delivery at the high temperature.
Because the force used for effecting substance delivery is an elastic return or restoring force, the drive, which operates against this return force, can be relatively small with small dimensions. This means costs reduction and reduction of the dimensions of the overall device.
An electric motor is preferably used as a drive. The electric motor is usually powered by a disposable battery or an accumulator. The device can be so designed that only a small motor power is needed for preloading the energy accumulator.
The device can include a transparent housing or housing parts. This enables an easy visual inspection of the operation of the device and of the amount of the substance in the container.
While the device, according to the present invention, was described with reference to its use as a lubrication device, it can be used, of course, for other purposes where a delivery of a predetermined amount of a liquid or viscous substance is required.